András Gáspárdy

AluI polymorphism of the bovine growth hormone (GH) gene, resumption of ovarian cyclicity, milk production and loss of body condition at the onset of lactation in dairy cows

Relationships among GH genotype (AluI polymorphism), parity, metritis and interval from calving to first ovulation, milk production and body condition score (BCS) loss were determined in dairy cows (n=307) on four large-scale farms in Hungary. Cows with systemic signs of puerperal metritis or mastitis were excluded. Time of the first postpartum (PP) ovulation was obtained from milk progesterone profiles. Based on GH genotype determination, groups of leucine homozygous cows (n=246) and valine allele carriers (n=61) were formed. All animals became cyclic during the study period. The average interval to first ovulation was 27.6+/-0.69-d PP (mean+/-S.D.). Genotype had no effect on the commencement of ovarian cyclicity. First ovulation occurred sooner after calving in pluriparous than in primiparous cows. The greater BCS loss cows had during the first 30-d PP, the longer they took to resume cyclic ovarian function. The interval from calving to first ovulation was substantially affected by farm, but not by mild cases of puerperal metritis. Genotype was not related to cumulative 30-d milk yield or BCS loss after calving. Primiparous cows had lower milk yield than pluriparous ones. Cows with metritis lost more body condition than healthy individuals in the first month postpartum. We concluded that, under field conditions, AluI polymorphism of the bovine GH gene had no effect on the interval from calving to first ovulation and could not be directly related to differences in milk yield and to the extent of BCS loss during the first month after calving in Holstein-Friesian cows.

Correlation between bull fertility and sperm cell velocity parameters generated by computer-assisted semen analysis

Motility is one of the most important characteristics associated with the fertilising ability of spermatozoa indicating their viability and structural integrity. Therefore, the examination of motility constitutes an integral part of semen analysis. Computer-assisted semen analysis (CASA) allows an accurate and objective assessment of different sperm motion characteristics with high repeatability. The aim of this study was to evaluate the different kinematic (velocity) parameters of frozen/thawed bull semen and determine if any of them could be correlated with their fertilising capability after insemination based on the achieved pregnancy rate. Ejaculates from 10 bulls were collected and frozen. The kinematic/velocity parameters of spermatozoa were measured by CASA and compared to the pregnancy results of almost 9,000 females artificially inseminated (AI) with frozen semen of any of the 10 tested bulls. The data of the experiments are summarised mainly with a focus on the effects of individual velocities (curvilinear velocity: VCL, straight-line velocity: VSL, average path velocity: VAP) on fertility rather than on the influence of progressive motility as a whole. We conclude that VAP is the most useful semen motility characteristic which has clinical relevance in the prediction of fertility.

Electronic monitoring of rumination activity as an indicator of health status and production traits in high-yielding dairy cows.

In view of the demonstrated relationship between rumination time and health status, the general welfare and metabolic condition of ruminants are often assessed by the examination of rumen function. The main goal of this study was to monitor the daily rumination activity (RA) and its connection with actual liveweight (LW), milk yield (MY) and with two diseases (subclinical hyperketonaemia - SHK, uterine disease - UD) in 96 cows on the basis of a total of 1638 observations in Israel. The studied sample gave a highly significant response, showing that the selected diseases had a diminishing impact on RA and LW and no influence on MY. It can be concluded that the change of RA as determined by electronic monitoring, complemented by the change of LW, is a useful general indicator of health status and subclinical disease before the appearance of clinical signs.

Involuntary reduction in vigour of calves born from sexed semen

The objective of this study was to compare the reproductive traits of heifers and the development characteristics of their calves following artificial insemination (AI) with sexed and non-sexed semen. The analysed characteristics included conception rate, gestation length, calf birth weight, calf vigour, stillbirth rate, and twinning rate. Data of 530 calves produced with sexed and 1,163 calves produced with non-sexed semen were analysed. The General Linear Model (GLM) was applied to assess the influence of semen type, farm, season of insemination, the calfs sex and the inseminating sire on gestation length and calf birth weight. With the exception of gestation length (P > 0.05), all other traits studied were significantly (P < 0.01) influenced by the type of semen. The conception rate was 55% for conventional and 44% for sexed semen, and the average gestation length was 274.6 and 274.9 days, respectively. The mean calf birth weight was 37.47 kg for non-sexed and 36.75 kg for sexed semen. The stillbirth rate was 6.19% for conventional and 7.54% for sexed semen, while the twinning rate was 3.78% for conventional and 1.13% for sexed semen. The calves produced with non-sexed and sexed semen differed significantly in viability (P < 0.001), the latter having a lower calf vigour score. The use of conventional semen did not affect the ratio of female and male calves (52.7:47.3%; P > 0.05); however, artificial insemination with X-sorted sexed semen significantly altered the sex ratio of calves (85.1:14.9%, P < 0.01). The results obtained in this investigation are in agreement with the majority of studies which compared the fertility traits, sex ratio and calf characteristics depending on the application of artificial insemination with sexed or conventional semen.

EVALUATION OF THE ON-LINE ELECTRICAL CONDUCTIVITY OF MILK IN MASTITIC DAIRY COWS

Mastitis is a persistent, inflammatory reaction of the udder tissue, which entails a decline in potassium, and is also responsible for a higher somatic cell count (SCC) and electrical conductivity (EC) of milk. The measurement of EC is an indirect, rapid method to detect subclinical mastitis from milk. The aim of this study was to analyse the EC of milk throughout the lactation, around the day of mastitis detection, and also to estimate its heritability based on data from a large-scale dairy farm. Shortly after calving the EC value generally decreases; however, it was discovered that from the thirteenth week onwards, substantial differences arise between the mastitic and healthy groups of cows. The authors observed a significant (P < 0.001) increase in EC before the detection of clinical mastitis. This higher value (around 11 mS) persisted for 4 days, then it gradually returned to the normal level. The EC of milk from daughters sired by different bulls responded differently in case of mastitis. The heritability of EC seems to be high (h2 = 0.56). Therefore, the EC trait can be a beneficial indicator in detecting mastitis and should be considered in sire selection.

Applicability of fetal thoracic aortic diameter measurement in the prediction of birth weight in Holstein-Friesian cows — Short communication

Transabdominal ultrasonography has been shown to be a useful and reliable method for assessing fetal well-being in horses and cattle. To test the applicability of fetal aortic diameter measurement in cattle, 44 late-term pregnant cows and heifers were examined 21 to 0 days prior to calving. Mean fetal aortic diameter was 2.07 ± 0.14 cm and mean fetal heart rate (FHR) was 109 ± 17 bpm. Three dead calves were dissected and their aortic diameter was measured in a water bath. The mean birth weight (n = 44) was 39.9 ± 5.8 kg. There was a significant negative correlation between FHR and fetal aortic diameter. However, although some studies have shown that fetal aortic diameter strongly correlates with birth weight in near-term horses and cattle, in this study there was no correlation between fetal aortic diameter and birth weight in Holstein-Friesian cows and heifers irrespective of whether the fetus was born alive or dead.